Download Atoms (“indivisible”)

Matter Epoch
(30,000 years - present)
Atoms (“indivisible”)
• 3 parts: protons, neutrons, electrons
nucleus
Atomic Number = # of protons in nucleus (defines element)
Each element can be found in different varieties (Isotopes)
Bohr Model
Binding Energy – energy required to keep an electron in its orbit
around the nucleus (depends on orbit size)
Neils Bohr discovered that electrons need to orbit the nucleus
with specific amounts of binding energy
Nucleus
• In other words, e- orbits can only be of certain sizes
• Orbit sizes are determined by the number of p+ in the nucleus
Electron States
Ground State – when all electrons occupy all lowest energy levels
H
He
C
All electrons want to exist in this state
Electron States
Excited States – when one (1) or more electrons occupy any orbit
beyond the ground state
- caused by an absorption of energy
H
He
C
- electron(s) will return to the ground state ! releasing energy
Electron States
Ionized State – when one (1) or more electron is removed from the
atom after absorbing and excess amount of energy
H
He
C
H+
He+
C+2
The “freed” electron(s) can recombine with the same atom or
another nearby atom.
Chemical Bonds
Two (or more) atoms can form new substances by bonding to each
other by sharing electrons (covalent) or exchanging electrons (ionic).
H
O
C
N
Molecule – two or more atoms chemically bonded
H2
O2
Compound – molecules made of two or more elements
H2 O
Organic Molecule – long chains of Carbon (life)
NH3 (ammonia)
Temperature
Measurement of the average energy of atoms within a substance
Low energy = Cold
High energy = Hot
Ways to increase energy:
- Add heat (e.g. light)
- Increase the pressure of the substance by adding more
force or shrinking the volume
States of Matter:
Matter will change states based on temperature (pressure)
Radiation Dominates Universe
Radiation can be described as a wave OR particle
Classical: combination of oscillating electric & magnetic field
Quantum: packet of energy (photon)
Waves
Wave – periodic disturbance of a medium from an equilibrium
condition that travels through space
Possible Media
• water
• air (sound)
• solids (earthquake)
Wave Properties
Velocity (v) – speed at which the wave moves
Wavelength (") – distance over which a wave repeats
Frequency (f) – number of waves that pass by a given point every
second (waves/second = Hertz {Hz})
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Photon Properties
Photon packet travels at c = 300,000 km/s
Photons are massless
Grouped according to wavelength, frequency, or Energy
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Inverse-Square Law
Luminosity – the total light output of an object (light bulb, star, galaxy)
Brightness – amount of light received by an observer
• depends directly on Luminosity
• depends indirectly on Distance to the star
Distance (d)
Light spreads over
1 L.Y.
2 L.Y.
3 L.Y.
L
B= 2
d
1 square
4 squares
9 squares
Reflection – the “bouncing” of light off of surfaces
Law of Reflection: Reflected angle = Incident angle
Refraction – the “bending” of light as it passes from one
medium to another
Planetary Properties
Semi-major axis (a) – average distance between Sun and planet
c
a
Eccentricity (e = c/a) – describes the “flatness” of the ellipse
Planetary Properties
Orbital Plane: “flat surface” that a planet’s orbit lies on
Earth’s orbital plane = “ecliptic plane”
Side View
Top View
Orbital Inclination (iorb) – angle a planet’s orbital plane makes with
respect to the ecliptic plane
Planetary Properties
Obliquity (#) – angle a planet’s equator makes with respect to the
planet’s orbital plane
Earth: # = 23.5º
Planetary Properties
Average density ($) – ratio of a planet’s mass to its Volume (m/Vol)
Material
Iron
Rock
Water
Oak
Air
Density (g/cm3)
7.86
2.0 – 5.5
1.0
0.6 – 0.9
0.0013
Albedo – the fraction (%) of sunlight reflected by a planet (0 – 1.0)
High albedo indicates: presence of an atmosphere
liquid/ice on surface of a planet
Planetary Properties
Equatorial Radius – a planet’s center-to-surface distance (size)
Oblateness – measure of the “flatness” of a planet (spherical = 0)
Planetary Properties
Surface Gravity – strength of a planet’s gravitational pull at its surface
- depends on a planet’s size & mass
Earth’s surface gravity
9.8 m/s2 (1 g)
Moon’s surface gravity
1.6 m/s2 (1/6 g)
Weight = mass x surface gravity
W = mg
Planetary Properties
Escape Velocity – speed required to escape a planet’s gravitational pull
Earth’s escape velocity:
11 km/s
25,000 m.p.h.
Planetary Comparison
Solar System planets are separated into two groups:
• Terrestrial (Earth-like) – Mercury, Venus, Earth, Mars
• Jovian (Jupiter-like) – Jupiter, Saturn, Uranus, Neptune
Property
Terrestrial
Jovian
Pluto
a (AU)
0.39 – 1.52
5.2 – 30.1
39.48
Porb (yrs)
0.24 – 1.88
11.9 – 163.7
248
e
0.007 – 0.21
0.009 – 0.054
0.25
iorb
0° - 7°
0.8° - 2.5°
17.1°
Req (Earth radii)
0.38 - 1
3.87 – 11.0
0.18
M (Earth masses)
0.055 – 1
14.5 - 318
0.0025
$avg (g/cm3)
3.93 – 5.52
0.69 – 1.64
1.1
Prot (days)
1 – 243
0.41 – 0.73
6.39
Oblateness
0 – 0.005
0.03 – 0.11
~0
Albedo
0.11 – 0.65
0.41 – 0.52
0.3
Earth
6,378 km
Radius:
Mass:
5.96 x 1024 kg
Surf. Gravity:
9.80 m/s2
5.52 g/cm3
Density:
Semi-major axis
150 x 106 km
Orbital Period
365.26 days
Rotation Period
23.93 hours
Composition: Silica (SiO2 based materials)
Metals (Mostly Fe & Ni)
Geology
Crust (3 g/cm3) - made of continental (granites) and oceanic (basalts)
Mantle (3 - 5 g/cm3) - 2900 km thick layer; location of lithosphere
& asthenosphere
Core (10.5 g/cm3) - liquid Fe/Ni shell surrounding solid Fe/Ni center
Hydrosphere
The collective mass of water on any planet (oceans, rivers, ice caps, clouds)
~ 70% of Earth’s surface covered by water
Atmosphere
Composition – Nitrogen (78%), Oxygen (21%), CO2 (0.037%), H2O (0.25%)
Ozone Layer ~ 25 km above surface
The Ozone Layer
Ozone (O3) absorbs UV radiation from the Sun.
UV
O3
UV ray breaks apart the O3 molecule
3 oxygen atoms recombine to form new O3 molecule
CFC’s can sneak in and combine with two oxygen atoms
! Ozone Layer depletes
The Greenhouse Effect
Visible light heats the surface; surface radiates IR; Greenhouse
gases (CO, CO2) trap IR within the troposphere; Tsurf = 15 ˚C.
Surface Features
Earth’s surface is changing continuously by many processes
Weathering - changes caused by the atmosphere
Sand Dunes
Pedestal rock: haloclasty
Surface Features
Erosion - changes caused by the hydrosphere
Grand Canyon
Cliffs
Tectonic Plates
Surface Features
Geologic - changes caused by plate tectonics
Convergent boundary: continental vs. continental
Mt. Everest
Surface Features
Convergent boundary: continental vs. oceanic
Volcano
Surface Features
Divergent boundary: seafloor spreading (ridge)
Mid-Atlantic Ridge, Greenland
Surface Features
Hot spots: regions of hot magma in the mantle that give rise to
volcanic (island) chains
Hawaiian Islands
Continental Drift
Over time, plate motions cause continents to drift apart and come
together (forming super continents, like Pangaea)
Magnetosphere
Dynamo Effect: moving charges in the outer core produce a
magnetic field around Earth.
Magnetosphere
• protects Earth from solar wind
• forms Van Allen radiation belts
• trapped particles at poles cause aurora
Aurora Borealis
Climate Zones
Warmer weather starts with greater amounts of sunlight heating
the Earth’s surface.
The amount of heating by sunlight depends on the angle at which
the light hits Earth’s surface.
Direct Rays
Oblique Rays
Direct rays concentrate more light on the same area which heats the
surface more
Climate Zones
Earth is not heated uniformly across the surface because it’s round
Rays are direct at equator & become less direct towards the poles.
Climate
If the Earth’s axis were not tilted, the amount of sunlight hitting
each latitude would not change during the course of the year.
No change in temperature means NO seasons.
Seasons
The tilt of Earth’s axis (23.5°) changes the angle that the sunlight hits
each latitude throughout the year.
Seasons
March 21st - Vernal Equinox
September 23rd - Autumnal Equinox
For Long Island observers:
Sun rises: Due East Sun sets: Due West
Noontime Altitude: ~ 50°
Seasons
June 21st - Summer Solstice
For Long Island observers:
Sun rises: North of East
Sun sets: North of West
Noontime Altitude: ~ 73.5°
Seasons
December 22nd - Winter Solstice
For Long Island observers:
Sun rises: South of East
Sun sets: South of West
Noontime Altitude: ~ 26.5°
Seasons
During the summer months the Sun stays above the horizon longer,
thus heating the surface more.
Tropic Zones (LAT
= 23.5° N/S)
(
The Sun will cross the zenith only for observers within the tropics:
- Tropic of Cancer (Summer Solstice)
- Tropic of Capricorn (Winter Solstice)
Arctic/Antarctic Circles (LAT
= 66.5° N/S)
(
These areas will experience continuous daylight or darkness for 24 hours
The Moon
Geologically inactive
Undetectable magnetic field
No atmosphere
Always see the same side of the Moon
Orbital Period = Rotation Period = 27.322 days
The Moon
Majority of our knowledge comes from 9 Apollo missions.
•Analyzed terrain from orbit.
• Apollo Lunar Surface Experiment Packages
(ALSEP)
• Collected 400 kg (800lb) of lunar samples;
! are in storage
Total cost: $100 per American, spread over 10 years
Craters
Formed by high speed impactors (meteoroids)
Mare
Lava filled impact basins that appear as smooth and dark terrain
Few craters found in maria because the
surface is young (3.4 Byrs old)
Mare Tranquillitatis
90% of Earth’s rocks are < 600 million years old
Highlands
Elevated regions formed by the build-up of debris scattered by impact events
Represents the original surface (4.4 Byrs old)
Tides
Moon’s gravity is NOT exactly the same at all points on the Earth
Differential gravitational force exerted by Moon creates a tidal bulge
Weakest
Strongest
Other influences on tides:
- Earth’s rotation
- Moon’s orbital inclination
- Earth not uniformly covered by water
- Oceanic currents
Sun influences the tides but to a lesser degree than Moon: Farther away
Lunar Phases
As the Moon orbits Earth our perspective of the light/shadow regions changes
Lunar Phases
Waxing phases
- right side of Moon is lit
- Moon rises/sets after the Sun
Waning phases
- left side of Moon is lit
- Moon rises/sets before the Sun
Eclipses
Light from the Sun casts a shadow in the following way:
Umbra:
Umbra dark, central shadow cast directly behind the object
Penumbra:
Penumbra lighter shadow on the periphery
Eclipses
Eclipses occur when the following conditions are met:
(1) Moon is in New/Full phase
(2) Moon at/near one of the nodes of its orbit
Eclipses
Solar Eclipse – occurs when Earth passes through the Moon’s shadow
Total: complete coverage of Sun; only seen where Moon’s
umbra hits surface of Earth
Eclipses
Partial: partial coverage of Sun; seen where Moon’s
penumbra hits Earth’s surface
Eclipses
Annular: Moon covers central part of Sun; Moon is
further from Earth so its umbra falls short
Eclipses
Lunar Eclipse – occurs when the Moon passes through Earth’s shadow.
Total: Moon in complete shadow
Partial: Moon moves through part of Earth’s umbral shadow
Eclipses
The Saros Cycle:
Cycle regular cycle of solar eclipses every 18yrs 11.3days
Precession
The Earth’s axis wobbles in space because the Moon’s gravity
pulls on the Earth unequally (26,000 years).
Effects of Precession
• Polaris will not always be the ‘pole star.’
• Seasons will “drift” through the months